A readme.md file at the project level will typically automatically be included as a None item,
which by default wouldn't pack either.

We should improve inference so that in this case, said file is automatically added as the package
readme file, if the project is being packed (IsPackable=true). We should also offer a property to
turn off this behavior just in case, with PackReadme=false in the inference targets.

NOTE: this should only exist in the Inference targets, so that when inference is turned off entirely,
this doesn't happen automatically, for consistency with other items inferences.